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Evolution of the Equatorial Atlantic from a continental transform zone into an oblique-divergent passive margin

Author(s): Renato De Matos FIXME, FIXME
Katya Casey
Ana Krueger
Ian O. Norton

he Equatorial Atlantic provides a unique opportunity to study the geometry, kinematics and deformation rates of the Earth's lithosphere during rifting with strong shear components along a series of long offset transform faults. Strike-slip basins of the Equatorial Atlantic formed during a break-up of the residual Gondwana land during Barremian between 126 and 120 MA along a 2,800 kilometers long intracontinental transform zone. During this period the intracontinental transfonn zone developed between the northern tip of South Atlantic rift and opened Central Atlantic which was drifting. Pernambuco and Paraiba basins were formed at the tip of the propagating South Atlantic rift. South America was rotating relative to Africa creating a pivot point in Equatorial Atlantic transform zone and transpression regime between present day Demerara and Guinea Plateaus. The South America-Africa transfmna zone behaved as a global-scale accommodation zone linking two propagating rupture fronts, located 3,000 kilometers apart from each other- the Central and Southern Atlantic sea floor spreading. Lithospheric keels and heritage left behind by the Neoproterozoic folded belts and cratons ofthe residual western Gondwana worked as anchors, preventing and divmting the continental rupture.

The fast (5-6 My) wrench deformation along the Equatorial Transform Zone was a result of a very large deeply rooted stress-buildup process, as Southern and Central Atlantic were rifting with different poles of rotation. The mode of deformation was directly related to the rate of deformation with neither mantle plume nor focused rift-path propagation in the region. When the stress buildup overcame the lithospheric anchor's resistance there was no time for crustal thirining. That is evident at the Pernambuco-Paraiba basins where a lithospheric “neck”

Evolution of the Equatorial Atlantic from a continental transform zone into an oblique-divergent passive margin
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